Go to System Preferences > Accessibility > Speech and set a keyboard shortcut, then you can turn any piece of text into an audio book by simply selecting it and pressing the text-to-speech keyboard shortcut. You'll need to set the Speaking Rate pretty high for this to be useful.
It works great for news, blog posts, HN discussions, and amazingly powerful proofreading tool for writers.
More info with screenshots here: https://docs.google.com/document/d/1mApa60zJA8rgEm6T6GF0yIem...